Drafting machine



A. L. BAKER DRAFTING MACHINE July 7, 1953 Filed March 22, 1950 3 Sheets-Sheet l INVENTOR ALLISTER L. BAKER ATTORN bodiment.

Patented July 7, 1953 UNITED STATES PATENT OFFICE f DRAFTING MACHINE Allister L. Baker, Denville, N J., assignor to Keuffel & Esser Company, Hoboken, N.J., a corporation of New Jersey Application March 22, 1950, Serial No. 151,287

This invention relates to a drafting head fora drafting machine. Reference is made to copending application Serial No. 6,789, filed February '6, 1948, now Patent 2,611,184, granted September 23, l952, of which this is a continuation in part. A fuller disclosure'of one of the embodiments mentioned in the parent case is given herein. Much of the structure shown in the parent case can also be used in the resent emherein has an advantage over the embodiment shown in the drawings of the parent application for some applications because the protractor is clamped positively to the protractor arm when laying off an angle- Various forms of drafting machines are well known in the art, such as, the pulley and band type, in connection with which this invention is useful. The usual type comprises a fixed member clamped to a drawing board, a first movable arm pivoted at one end to the fixed member, a second movable arm pivoted at one end to the moving end of the first arm, and a drafting head carried at the free end of the second movable arm and movable over the drawing board. The drafting head includes a protractor and a protraotor arm with means for holding one or more scales, rulers, or s traightedges, which can be rotated about the protractor. As the drafting head is moved over the drawing board, orientation of some member of the protractor or draft ing head is held constant by a combination of pulleys and'bands, parallelograms or the like. The present invention relates only to the draftin head and it should be understood that the form of the other parts of the machine in no Way affects the invention.

Specifically, the invention relates to an improved type of drafting head which may be combined in any suitable manner, known in the art, with othe parts necessary to form a drafting machine.-

- The principal object of the invention is to provide a drafting machine head which is particularly useful for performing the operations required in making maps and the like.

Another object of the invention is to provide in a drafting head means for making extremely fine adjustments when setting the protractor arm to selected angles or to a selected base line.

Another object of the invention is to provide a Vernier or index mark plainly visible at all positions of the protractor arm.

A further object of the invention is to provide a fully covered and protected protractor scale.

However, the embodiment described These and other objects of the invention and the means for their attainment will be more apparent from the following detailed description taken in connection with the accompanying drawings illustrating the invention,,and in which:"

Fig. I is a View in plan of adrafting machine provided with the newhead. I g

Fig. II is an enlarged View in plan of the drafting head. 1 1

Fig. III is a view in sectional elevation of the scale frame and tangent screw arm taken along the line III lII of Fig. II and'looking in thedi rection of the arrows. g

Fig. IV is a view in sectional elevation taken along the 'line'IV-IV in Figs. I and IIlooking in the direction of the arrows butshowing' the magnifying lens rotated 90 from its positionin Figs. I and II and showing the clamp 14 in-the dotted position of Figj' II for purposes of illustration only.

Fig. V isa view in enlarged sectional elevation taken along the line V'V of Fig.IV and looking in the direction of the arrows. I

In Fig. I, the fixed member or anchor '2-is provided with means for'clamping it to the 'drawin board. The first movable arm 4 is pivoted to this member 2 at one .end and to the second I movable arm 6 at its other end. The drafting head 8 is at the free end of thesecond movable arm 6.

As shown in Fig. IV, the band l2 passes around the drafting head" pulley ID. A ball bearing l4 provides frictionless rotation means'between the drafting head pulley l0 and'the head'bracket l of the second movable arm 6, so that the arm may rotate with respect'to the pulley which is held in orientation bythe band [2. The inner race of the ball bearing [4 is held onto thesleeve H of the drafting head pulley II] as by the nut IS. The outer race is attached to the head bracket 1 in this embodiment by a press fit.

The center stud or pivot pin IB is fr'eeto turn inside the'drafting head pulley I0 and is accu rately centered therewith being in close bearing contact with an internal bearing surface of the sleeve. ll of the'drafting head pulley ID. The lower end of the center stud l3 has two portions 20 and 22 of different outside diameter. The protractor arm 26 fits over the portion 22 of center stud I 8 and is fastened to the portion 20 as by the screws 23. The protractor arm 26 may be provided with chucks or other means to receive one or more rulers, scales, or straightedges 21. The tangent screw arm 32 also fits over the portion 22 and is separatedfrom the protractor arm by the washer- 34.- The center screw, 36 engages threads in the portion 22 to hold the tangent screw arm 32 on the stud in such a manner that it is free to rotate about the stud. The center screw 36 also acts as a glider on which the drafting head rests as it is moved over the drawing board.

A holding member 24 is secured to the drafting head pulley 50 by the screws 25. The annular member or limb plate 28 provided with a protractor scale 92 fits over an outer cylindrical surface on member 24 and is held in frictional contact with the lower surface of the drafting head pulley Ill. The spring washer 30 acts between an upper surface on the member 24 and a lower surface on the annular member or limb plate 28 to increase the friction between the annular member 28 and the lower surface of the drafting head pulley ill.

The upper end of the center stud i8 is provided with a portion 38of smaller outside diameter and a threaded portion 46 of still smaller outside diameter. The knob support 42 fits over the portion 38 of the stud l8 and is keyed thereto by the key 44. The center nut 46 engages the threaded portion 40 of the center stud i8 to hold the knob support 42 and the center stud rigidly together. The knob 48 fits over the knobsupport 42 and is held rigidly thereto as by the screw 50.

A magnifying lens 52 is held by the magnifying lens arm 54 which "is provided with a hole fitting over the sleeve I I which is an integral part of the drafting head pulley H1. The magnifying lens arm 54 is held in placeon the sleeve ll by means of the retaining ring 56. The action of the retaining ring 56 is such that the magnifying lens arm 54 remains oriented with the drafting head pulley l9 and remains over the index mark or Vernier 94 in normal use of the drafting machine. The magnifying lens arm 54 may be turned by hand about the sleeve 1 I if it is desired 2 to change itfrom a reading to a non-reading position. V The annular cover plate 58 is fixed to the drafting head pulley to which it may be fastened directly or through the ring 5'! as by screws 69 and 64. The annular cover plate 58 is preferably of a transparent non-fragile material such as a plastic but it may also be constructed of an opaque material having a cut out or transparent portion at the. position of the Vernier 94. The Vernier or index mark 94 is provided on the ring 5'! which is held in orientation by the drafting head'pulley, v V

The protractor holding plate 66 is fastened to the limb plate 28 by means of the ring 68 and screws 1'0.- The pin 12, the lever arm 14 and the springs 16 and 11 (see Fig. V) comprise a clamp for clamping the protractor holding plate 66 and thereby the annular member or limb plate 23 with its protractor scale 52 to the protractor arm 26.4 The pin 12 is slidably mounted in a hole in the protractor arm 26. pin 12 is threaded to fit a female thread in the lever arm 14. The springs 16 and 1'! act between the protractor arm and the pin12 to hold the pin- 12 up out of engagement with the protractor holding plate 66. The set screw 75 prevents rotation of the pin I2. V 7

If the lever arm 14 is rotated in one direction it pulls the pin 12 downward against the action of springs 16 and 11 to clamp the protractor holding plate 66 against theprotractorarm 26. If the lever arm is moved in the opposite direction the pin T2 is forced upward by springs 16 and T! The lower part'of the 4 out of contact with the protractor holding plate 66.

In Figs. II, III and IV, the tangent screw 18, clamp screw 80, locking lever 82, tension spring 84, and other minor parts to be described form a clamp and tangent screw arrangement for fine adjustment of the protractor arm 26 or thereby the protractor 92. The locking lever 82 is provided with a female thread which engages with the clamp screw so that when the locking lever 82 is pushed in one direction it pulls the clamp screw 89 downward against the annular cover plate 53, clamping it between the clamp screw 80 andthe bracket 86 which is an integral part of the tangent screw arm 32. The clamp screw 80 is pinned to the bracket 86 by the set screw 88 to prevent its turning when the locking lever 82 is actuated. The head of the clamp screw 80 is provided with several holes spaced equally in a circle, The set screw 88 will fit each of these holes so that in the event that the clamping ac.-

tion' becomes loose it may be tightened by turn.-

female threaded member 90 against the projec The point of tion 91 on the protractor arm 25. the tangent screw held in contact with the projection 34 of the protractor arm 26 by the tension spring 84 acting between the t-angentscrew arm 32 and the screw 25cm protractor arm 26.

When the clamp is closed by the locking lever 82, the tangent screw gives a fine adjustment to the protractor arm either for adjusting the protractor arm 25 or the protractor ,92 (if the latterlis clamped to the protractor arm by clamp 74) relative to the drafting head pulley. The tension spring 84' holds the tangent screw arm 32 and the protractor arm 25 together so that they act as one except when the tangent screw is used to give afine adjustment. I. v

; '-I-he tension spring 84 is so positioned that it cannot be extended when drawing lines due to pressure exerted against the straight edge 27 by the drawing instrument. Such pressure will only increase the pressure between the point of the tangent screw 18 and the projection 92 of the protractor arm 26.

When the locking lever 82 is closed, it locks the tangent screw arm 32, by means of the bracket 86, to the annular cover plate58. Since the am nular cover plate is fastened to the drafting head pulley Iii, the effect of the clamping action is to lock the tangent screw arm 32 and thereby the protractor arm 26 to the drafting head pulley it.

The'limb plate 28 is provided on its upper .surface with a protractor scale 92 extending through the full 360. The annular Vernier plate 51 is provided on its upper surface with an index mark or preferably a VGIIllBIi scale 94, one of the lines of which may be considered an index mark lining up with the protractor scale 92. The divisions of the protractor and Vernier scales are chosen to read angles to any desired accuracy consistent with the inherent accuracy of the parts of the machine. In the preferred embodiment of the invention the protractor scale is divided to divisions representing 30 minutes and the Vernier is divided to read theprotractor scale to one minute, although a coarser arrangement is'indicated A line may be drawn to any angl'ewith jre's'pect' to the base line to which'the protractor hasb'e'e'n set as follows. With clamp'l l-clos'ed andfcla'rfip 82 open, the protractor arin" 2B is-turned until the desired angleonithe protractor'tz is adjacent to the Vernier scale 94. Since the verriiersc a does not move with the'protractonarmit isih'ot necessary for the operator to move'his head when finding the angle. The armrnaybe setgmor accurately to the desired angle, by clamping the tangent screw arm 32 to the drafting head pulley Ill with the locking lever82 and making a'fin'e adjustment of the protractor arm carrying the protractor 92 by means of thetangent screwflil'. Having thus set the protractor arm to the desired angle, the drafting head 8, may be moved over the drawing board. Thecombination of bands and pulleys maintain the orientation or angle folf the scale or straightedgell on the protractor arm, 26. protractor arm passes through a desired point, the line is drawn at the selected angle through this point. By moving the draftinghead again, lines may be drawn through any other desired points atthesame selected angle, Lines-.may be so drawn throughany.desiredjpointsat any otherdesired angle to the same base line by resetting the protractor arm in the manner described.

If it is desired tochange ,to another base. or reference line and make the zero setting ofthe protractor correspondto this lineon thedrafting board, this may be accomplished asv follows. With clamp 14 closed and clamp 32 open, the .protractor arm is rotated until the protractor read ing on the Vernier 94 is .close to zeroJ, Then the locking lever 82 is pushed back to clamp .the tangent screw arm 32 to the drafting head pulleyyl o, so that the protractorarm carrying .the protrac tor may be adjusted to make the reading Qof-Ythe. protractor andvernier.scales exactlyaero.

Theclamp I4 is then opened. This fixes th limb plate 28 to the drafting head because of the action of spring washer'fab maintaining the zero setting of the protractcr 9 2, to thevernier fl; The clamp 82 is opened and the protractorl arm ZEis rotated and if necessarythe drafting head is moved over the drawing board until--the straightedge 27- isparallel to or in coincidence. with the desired reference-or baseline. g lfjthe. locking lever 82 is again closed to clampthetan gent screw to the drafting head pulley 'the pro-' tractor-arm 26 can be given a fine adjustment by means of the tangent screw "58, to set the straightedge exactly on or parallel to the desired reference line, without disturbing the zero setting of the protractor. The clamp 14' is then closed. The protractor then will be moved with. the protractor arm 26. The clamp 82 is then. released and the machine is ready for laying off angles from the new reference or base line as previously 1 described.

The invention has been described as applied to the art of drafting machines. This art, as is understood, includes not onlyen gineering' or architectural drawing and the like but also mapping or surveying. In the latter fields a drafting machine or angle plotting machine of high accuherein is of special value.

The, invention has been described with refer ence to anembodiment having a protractor' scale $2 on annular member 28' and an index mark 9k on'member'tl carried by the member maintainedin orientation or drafting pulley 10. "It will be realizedthatan equally-useful embodiment is'ob-j tained if the protractor scale is provided on mam:

racy and ease of operation such asdescribed-"- berfi'l' carried by the drafting head'pulley and the vernier or'index mark is providedon annular member "28. The advantage of the former con struction isthat-the index mark would never be;

When a straightedge attached to the come hidden under 'thearmfi. The advantage of the latter construction is that the angular relations between-objects-drawn on mapsandthe'lik'ewill be more readily apparent. i What is claimed is: H "1. In a drafting machine for ;use on a drafting board, a drafting head comprising; a member maintained in orientation on the drafting board, a protractor arm' for carryingfat i least one straightedge rotatable withrespect to said member maintained in orientation, an annular member alsofirotatable with respect-to said memberi maintained in orientation but having a surface in frictional contact witha surface of, said member maintained in orientation, ,resilientm'eansi applying constant frictional forces between said surfaces, said frictional forces beingof sufficient magnitude so that said 'a'rinularmemberwill remain 'fixed to said member maintained in orientation during free rotationof j said proftractor: arm, cooperating index mark and: pro-1 maintained in orientation and said annular me ber, means for clamping said annular member to said protractor arm to move it with respect to said member maintained in orientation against;

frictionand a clamp acting between said prof tractor arm and said member maintainediin orientationto fix said. protractor arm at any selected angle.

I 2.;In a draftin machine-foruse on a drafting. bo'a'rd,fa drafting head comprising a member maintainedfin orientation on the drafting board carrying an index marl r, a protra'ctor arm for. carrying atleast one straightedge rotatablewith respect to. said member maintained in orientation, an annular, member carrying a protractor scale cooperating with said index mark alsov rotatable with respect to said member maintained in orientation but having a'surfacein frictional C nt ct witnajs rface ofsaid member main-Q .tained in orientation, resilient means applying.

constant frictional forces between said surfaces, said frictional forces being of suflicient magnitude so that said annular'member will remain fixed to said member maintained in orientation during free rotationof said protractor arm, means for clamping said annular member to saidpro: tractor arm to move it with respect tosaid meme benmaintained. in orientation against; frictionv and a clamp acting between said protractor. arm

- and'said member maintained inorientation to,

iixflthe protractor arm at any selectdangle. 3: In a drafting machine for useon a dr'afi-l ing board, aidrafting head comprisinga mem ber, maintained in orientation "onthe drafting boardpa protractor arm for carrying at least one straightedge rotatable with respect .to saidrhember. maintainedin. orientation, an annular. member also rotatable with respect to said member maintained in' orientation but having a surface in frictional contact with a surface of said member maintained in orientation, resilientmeans holding said surfaces in frictional con-, tact, coperating index mark and protractor scale means carried by said member maintained in orientation and said annular member, means for clamping said annular member to said protractor arm to move it with respect to said member maintained in orientation against frietion, a clamp acting between said protractor arm and said member maintained in orientation to fix said protractor arm at any selected angle and fine adjustment means for setting said protractor arm accurately with respect to said member maintained in orientation;

'4. In a drafting machine for use on a drafting board, a drafting head comprising a member maintained in orientation on the drafting board, a protractor arm for carrying at least one straightedge rotatable with respect to said member maintained in orientation, an annular member also rotatable with respect" to" said member maintained in orientation but having a surface in frictional contact with asurface of said member maintained in orientation, resilientmeans holding said surfaces in frictional contact, cooperating index mark and protractor scale means carried by said member maintained in orientation and said annular member, a knob centrally located above said annular member and fastened to said protractor arm for turning it to any selected angle, a transparent cover plate carried by said member maintained in orientationand covering said protractor scale and index mark, means for clamping saidannular member to said protractor arm to move. it with respect to said. member maintained in orientation against friction, a clamp acting between said protractor arm and said member maintained in orientation to fix said protractor arm at any selected angle and fine adjustment means for setting said protractor arm accurately with respect to said member.

maintained in orientation.

5. In a drafting machine for use on a drafting board, a drafting head comprising a member maintained in orientation on the drafting board, a

protractor arm for carrying at least one-straight-.

edge rotatable with respect to said membermaintained in orientation, an annular member also rotatable with respect to said member maintained in 'orientation but having a surface in. frictional contact with a surface of said. member maintained in orientation, resilient means applying constant frictional forces between saids'urfaces, said frictional forces being ofsufiicient magnitude so that said annular member will remain fixed to said member maintained in orientation during free rotation of said protractor arm, cooperating index mark and protractor scale means carried by said member maintained in orientation and said annular member, a thin flat annular plate secured to said annular member, a clamp means for bending said thin fiat annular plate into contact with a surface of said protractor arm to clamp said annular member to said protractor arm so that it may be'movedtherewith against friction and a clamp acting between said protractor arm and said member maintained in orientation to fix said protractor.

arm at any selected angle.

6. In a drafting machine for use on a drafting board, a drafting head comprising a member maintained in orientation on the drafting board, a protractor arm for carrying at least one straight-.

edge rotatable with respect to said member main--; tained in orientation, an annular member also rotatable with respect to said member maintained in orientation but having a surface in frictional contact with a surface of said member maintained in orientation, resilient means holding said surfaces in frictional contact, cooperating index mark and protractor scale means carried by said member maintained in orientation and said annular member, means for clamping-said annular member to said protractor arm to move it with respect to said member maintained in orientation against friction, a tangent screw arm rotatable about the central axis of said drafting head, a female threaded member threaded in a direction tangent to a circle hav-. ing its center on the central axis of the drafting' head carried'by said tangent screw arm, a tangent screw engaging said threaded member and projecting against said protractor arm, a spring in tension acting between said tangent screw arm and said protractor arm holding said tangent screw in contact with. said protractor arm and a clamp for clamping said tangent screw arm to said member maintained in orientation to fix the protractor. arm at any selected angle and so that when said clamp is closed said tangent screw will serve as fine adjustment means for setting said protractor arm accurately with respect to said member maintained a in orientation.

7. In a drafting machine for use on a drafting board, a drafting head comprising a member maintained in orientation on the drafting board, a protractor arm for carrying at least one straightedge rotatable with respect to said member maintained in orientation, an annular member mounted concentric to said member maintained in orientation, cooperating index mark and protractor scale means carried by said member maintained in orientation and said annular member, means for clamping said annular member to said protractor arm to move it with said protractor arm with respect to said member maintained in orientation, said annular member and said member maintained in orientation being in constant frictional engagement with each other,

resilient means held by said members under a fixed predetermined unadjustable stress, said'resilient means applying constant pressure between said annular member and said member maintained in orientation to produce constant frictional forces between said annular member and said member maintained in orientation, said frictional forces being of sufiicient magnitude so that said annular member will remain fixed to said member maintained in orientation during rotation of said protractor arm when said clamping means are open. I V v ALLISTER L. BAKER.

References Cited in the file of this patent UNITED STATES "PATENTS Number Name Date 2,164,218 Little June 27, 1939v 2,394,344 Wallace Feb. 5, 1946 FOREIGN PATENTS Number Country Date 496,573 Great Britain Dec. 5, 1938. 837,367 France .4 Nov. 12, 1938 884,222 France Apr. 19, 1943 

